LiteOn PA-6601-1A (600w) blows its TOP

[Пофигист]

Re: LiteOn PA-6601-1A (600w) blows its TOP

For 10 years, someone will lay out the scheme ...?

[Eldip]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Thanks for the replies! and Happy New Year

Attaching pictures of the board to show you what I mean. I believe the SOP8 mosfets marked A2700 are not on the mains side - I meant they are on the primary side of the step-down transformer for the output voltages (which is all on the secondary side of the PSU).

The A2700 mosfets are components Q306A-Q309B (8 in total), but it's only Q307A & Q307B that were overheating (Q307A is removed in the pic, Q307B is seen there hand-soldered). The heatsinks above Q306A-Q309B were removed but the missing heatsink doesn't account for the speed at which Q307A & Q307B were overheating.

I've made progress since these pics were taken. Most embarassingly I discovered a solder splatter which was shorting out a few components near the power factor corrector (see photo). On removing the solder I replaced Q307A & Q307B again... and while they are still getting much hotter than the other A2700 SOP8 mosfets, they are not blowing their tops anymore... and now with their heat sync re-installed and the PSU fans running they don't seem all that hot for major concern.. (hesitant yay!)

I did my best to investigate the circuitry around Q307A & Q307B but did not find anything broken, though I may have missed something. D306 (marked "BM" - see photo) appears to be a SMBJ15A General Semiconductor unipolar Transient-voltage-suppression diode (TVS), and because it does not pass the DMM diode tests it had me thinking it was broken until I took it out of circuit and tested with a current limited benchtop power supply. It seemed to hold the current back until it reached the breakdown voltage.. first time testing a TVS but I think D306 was ok after all.

So now all the output voltages are good (12V, -12V, 5V, 3.3V), and it all seems working, although I don't have any system to test the PSU with unless I pull apart a working Powermac (frustratingly, the G5 Powermacs these PSUs are for require removal of the 2 CPUs in order to replace PSUs!).

I would appreciate thoughts on one question: R304 (see photo) is a 750R, fused 3W resistor and while the PSU is idling R304 is too hot to touch. I want opinons as to whether this is acceptible or a sure sign of an unresolved problem with the circuit. I'd say the temprature of R304 is at least 100C, (isopropyl alcohol evaproates almost instantly when sprayed on it, though it is not so hot that it is causing any burn marks on the board). There is 38V across the resistor when the PSU is idling. I'm not very experienced at using electronic equations in practice but it is my understanding therefore that the resistor is dissipating ~2W, given the formula: V * V/R = P .. i.e. 38 * 38/750 = 1.92W.

2W is under the 3W rating of the resistor, but my question is whether this is perfectly acceptible or is this hot resistor a sure sign of an unresolved problem with the circuit?

If it's acceptible then I can put aside the PSU as fixed, otherwise I may need to put it aside until I can eventually aquire a second PSU (same model) to compare this one with for reference.

In addition to my pics there were lots of useful pics of the same board posted back at #48 https://www.badcaps.net/forum/showpo...6&postcount=48 and #74 https://www.badcaps.net/forum/showpo...6&postcount=74

Appreciate your thoughs!

[Agent24]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Maybe he meant SOIC package? That may be okay for high voltage depending on the pinout and circuit design - some integrated PWM/FET chips run in a SOIC-8 package (albeit often with only 7 pins) for small SMPS like a cellphone charger etc.

[PeteS in CA]

Re: LiteOn PA-6601-1A (600w) blows its TOP

I suggest finding out - maybe even drawing a partial schematic - where Q307A & B are in the circuit and what they do. I could be wrong, but I'm not sure the SOP-8 package is suitable for high voltage or high current.

[Agent24]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Do those MOSFETs switch mains?

Probably when those original ones blew, they shorted and damaged their drive circuitry (or it contained the original fault).

Now with damaged drive circuits, the new MOSFETs are not switched properly and fail quickly. You may also have bad snubber circuits (if present).

[Eldip]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Greetings! and sorry for the necromancy but I read somewhere back in this thread something to the effect that threads never die they're just sleeping...

I've been struggling with a broken LiteOn PA-6601-1A for a long time now, enjoying this thread repeatedly, as each time I order parts it's usually months before my next repair attempt.

When I received the unit C301, C302, R302, Q301 were all damaged so have now been replaced.

However now when I start the PSU by shorting pins 14 & 23 with a paperclip. Q307A & Q307B burn out. These are SOP-8 output mosfets marked A2700 and I believe are on the primary side of the stepdown xformer. The PSU fans spin up and all sounds good but Q307A & Q307B overheat quickly. I replaced them and they blew again.

I sincerely appreciate the gentle reminders throughout this thread to build a current limiting lamp, which has been invaluable with many projects since. And with this unit Q307A & Q307B still burn out but they do so much more slowly

I'm doing my best to find any reason for the issues with the overheating Q307A & Q307B but haven't any luck so far..

Anyone with any fond memories about this PSU have suggestions of what I should look for/test?

[Agent24]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Sometimes parts which switch high voltages or currents just fail from old age and stress.

[reessi]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Many thanks to everyone on this thread, just repaired one of these - TOP/Q856 & the OPTO.

So I'm curious does anyone know why the TOP blows? The cap has been mentioned but mine checked out fine on Capacitor meter and an ESR meter! And computer powered fine! Should I still change it? I am going to anyway in case it goes bad soon! Ordered some new ones.

Cheers.

[fichamba]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Hi everybody, and thanks for all of your comments.

I had one of this SPSUs from a MacPro absolutely blown. F1 was open, and of course, when you installed a new 10A/250V fuse, it died again.

Finally, I was able to fix it, and I want to share it here with you, just in case my comments will be of any help like yours. All of us know that there are subtle differences when you are having the same failure, so here are my conclusions:

I began with the shorted Q301...of course. By the way, it was very easy to buy some of them in Farnell.

You have no way to check U801 and U802, so I changed it also.

C206 & C208 caps (4.7uF/50V) were low in value out of circuit (app. 2uF), so I changed them by a new, fresh ones.

R302 (100 ohms/5W...sorry, not 2W as I have readed here...), was open, so I changed it also. It acted as a fusing resistor for Q301, obviously.

Checked the 8 output mosfets (Q308A-B, Q309A-B...etc.), and all seemed OK. Not shorted.

So I decided to apply AC to the SPSU input (via a variac, just in case...). Well, with a DMM between green wire and one of the black ones, and without install a jumper between green and black wires, I had a DC voltage reading of some 5V. Well, so far, so good.

Them, I decided to make a short between green wire and GND. Oh my!. The fuse in the variac was blown inmediately, and after discharging all primary caps, I checked that my costly Q301 was absolutely shorted.

Installed a new Q301, and decided to check for shorts (great shorts) at the output stage. And of course, a more detailed inspection, component by component.

Well, in my particular case I found a shorted Q305 (output mosfet, 50V/80A). Originally, it uses the now obsolete SUP85N06-05. I installed the new SUP90N10-8M8P-E3 instead. There were more: C301 & C302 (more than 10 times less in value).

After a careful inspection, I decided to apply power again thru the variac. Tha SPSU worked perfectly. Apart from Q305 -shorted- it was extremely important to change C301 & C302. If they are out of value, R302 begins to smoke.

I hope this can be of help for some of you, like your comments were for me.

Thanks again, and good luck. SPSUs are heavy to repair most of the times.

[Toasty]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Go to the Main forums page.

Scroll down to the Motherboards section.

Choose one of the sections that best fits your brand of board.

Click the New Thread button at the top left in that subsection.

Best describe your make/model in the title to draw folks in. List problems and why you think that cap is bad.

T

[wasureppoi]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Hi,
I tried to start a new thread clicking on "New Posts" but nothing happened. Is there a different avenue I should be pursuing as you seem to indicate I can start a new thread.

Sorry for any inconvenience.

Regards

[Toasty]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Start a new thread please. This is not about a motherboard.

[wasureppoi]

Re: LiteOn PA-6601-1A (600w) blows its TOP

This is definitely at odds with the original post but I wonder if anybody would be able to interpret anything meaningful to some values on a capacitor on a motherboard:
LF100 C893
In the 2 pics I have uploaded the "pink" insitu capacitor is about twice the size of the "blue" one. I could obtain the former but have struck a brick wall with the latter.
Any assistance would be greatly appreciated.

[Toasty]

Re: LiteOn PA-6601-1A (600w) blows its TOP

#1 - use the lamp in series trick to stop blowing components:

https://www.badcaps.net/forum/showpo...2&postcount=23

Haven't touched this in a long time. I think I have it around somewhere. Just gave up after a while. Easier to buy a working unit on ebay.

T

[Flubr]

Re: LiteOn PA-6601-1A (600w) blows its TOP

I had the problem with R302, F1, C301, C302, Q301, Q352 and D355. In a first attempt to fix the supply, I replaced these components. However, the fuse blew again and MOSFETs, transistor and diode failed again.
After some iterations, I discovered that also Q305 was broken (replaced with CSD18532).
In my latest attempt, I also replaced a bunch of other components: U351 & U352 (MIC4424 or UCC27524), the 5 optocouplers, the TOP249, Q302, C303, U401 & U501 (SN74HC02). For Q301, I found SIHP24N65 as a replacement.

However, the problem is still not solved. I get 25V in standby, but on power up, the fuse blows, together with Q301, Q352 and D355. I couldn't find any other failed components. Does anyone have an idea or suggestion?
I would like to know the normal series resistance of L1, so I could check if it's still okay.

[Toasty]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Threads are always open, unless a flame war erupted and the admin closed it with rusty nails. LOL

Provided it's on topic, we'll gladly jump back in.

T

[keithf2]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Are any of these threads still open

[wasureppoi]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Beg your pardon. Wish I had those links earlier but managed to get the chips I sought but I had read your post out of context and thought you were referring to complete PSU's! Thanks anyway.

[Toasty]

Re: LiteOn PA-6601-1A (600w) blows its TOP

http://www.ebay.com/itm/190798671136

http://www.ebay.com/itm/120920844464

http://www.ebay.com/itm/110990867455

[wasureppoi]

Re: LiteOn PA-6601-1A (600w) blows its TOP

Ebay has them from Hong Kong.

T

Hi,
Looking on Ebay here nothing comes up and even www.ebay.com.tw
reveals nothing. Do you think you would be able to send me a link or do you think they are all long gone?

Regards,